On the PHP-GTK Community site today, there's a "quick hit" post for extending a GtkMenu object in a PHP-GTK application to create a popup menu dialog.

Here is a quick way to build a popup menu supporting event registration from a GtkWidget. Menu items are passed to the class constructor as a list of labels. This class emits activate signals with full context (x,y coordinates, button ...).

There's the list of the steps that the code will follow and the two code chunks that will make it happen - the sample PHP-GTK app and the class file that handles the menu creation.